Geoff Wearmouth
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warmtoffee.bsky.social
Geoff Wearmouth
@warmtoffee.bsky.social
71 followers 24 following 100 posts
Press plastic for a living but love the touch of rubber. Assembler of Gosh Wonderful and Looking Glass ZX Spectrum ROMs.
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Reposted by Geoff Wearmouth
exeter.ox.ac.uk
It is with great sadness that we share the news of the death of Prideaux Fellow David M. Webb MBE (1983, Mathematics), who passed away yesterday.

David was a distinguished Exonian whose legacy will not be forgotten.

🔗 Read the Rector's tribute: https://ow.ly/hhMa50XWF52

#ExeterCollegeOxford
David M. Webb MBE (1983, Mathematics)
January 14, 2026 at 1:45 PM
Reposted by Geoff Wearmouth
spectrumcomputing.bsky.social
Happy New Year! ✨

Looking back at 2025 — a great year at SC:

• 25 new updates of ZXDB
• 8 major releases of new website features and fixes
• 2,200+ videos re-created from the lost RZXArchive YouTube channel

🚀 2026 - looking forward to service the ZX Spectrum community - and related machines 😘
January 2, 2026 at 12:10 AM
Reposted by Geoff Wearmouth
righto.com
Intel announced the 8087 floating-point chip in 1980. Now I have a blog post that explains a small part of the microcode in this chip.
www.righto.com/2025/12/8087...
Conditions in the Intel 8087 floating-point chip's microcode
In the 1980s, if you wanted your computer to do floating-point calculations faster, you could buy the Intel 8087 floating-point coprocessor ...
www.righto.com
December 30, 2025 at 7:54 PM
warmtoffee.bsky.social
Did you know that the first instruction in the ZX Spectrum ROM is DI - Disable Interrupts. Quite a dramatic entrance. The DI instruction was not used in the ZX80 and ZX81.
Here is my ZX80 assembly listing from 2002. I tried to use the Logan O’Hara labels when apt.

web.archive.org/web/20150501...
Assembly Listing of the Operating System of the Sinclair ZX80.
web.archive.org
December 20, 2025 at 2:22 AM
warmtoffee.bsky.social
How to set your ZX Spectrum to 10:00 am. Make it pause for twenty minutes.
December 20, 2025 at 2:12 AM
warmtoffee.bsky.social
The ZX Spectrum has accurate integers using binary logic. After any decimal point, every digit is converted into an inaccurate recurring binary which is then added to the running total. This is fuzzy logic and all the duds average each other out so that half the time the number is correct. #fuzzy
The picture shows the recurring binaries that The Spectrum uses for the first digit after the decimal point. For the next and every digit there is a similar set of recurring binaries. The chances of these averaging out to the correct mantissa are surprisingly high - about 50%. Not good enough for collecting the 34th bit during division for instance. The author states in the source code that multiplication is adapted from the Zilog Developer Library. Not so the division as there is a bit missing in more than one way.
December 16, 2025 at 11:46 AM
warmtoffee.bsky.social
Wow! The source code for the ZX Spectrum has been posted to the Internet Archive by Timex Computer Corp. see my other posts.
Right at the end where the 7 byte “ROOT:” routine is Steven has written “***REPLACE WITH NEWTON-RAPHSON SQUARE ROOT***”
I used it in the SG03.rom for the ZX81 and now BL81.
At the end of the ZX Spectrum ROM, Steven Vickers wrote to replace the small but slow TO_THE: routine with a fast accurate NEWTON-RAPHSON routine. Get my binary logic LOOKING GLASS ROM to experience this on a Spectrum (from speccy4ever and spectrumcomputing.co.uk)
December 11, 2025 at 6:39 PM
warmtoffee.bsky.social
Did you know that the Complete ZX Spectrum source code has been uploaded to Internet Archive by Timex. It was written by Nine Tiles on Zilog Development Studio and Timex obtained the same software.
A bit dry but there is a FART joke in there. See the last file.

archive.org/details/time...
The System Variable that controls the CYCLES OF ERROR NOISE has been named FART, later RASP, probably because when his parents took him to see what they had been working on he saw a computer that blew a Raspberry when there was an error. This page contains the Z80 code that dumps the display file to the ZX Printer. The editor shown is the Zilog Development Studio as used by Nine Tiles and Timex Computer Corp. Thanks to engineer Lon Hildreth for making this available. Here are messages such as the dreaded “R: Tape loading error” and also “(c) 1982 Sinclair Research Ltd.” This page of source code documents the INPUT command which inputs from stream 1. It loads the accumulator with 1 and then calls subroutine SELECT. It then clears the lower screen which sets the stream to zero again. Hint: Just swap the two instructions.
December 8, 2025 at 9:17 PM
Reposted by Geoff Wearmouth
xkcd.com
Website Task Flowchart

xkcd.com/3175/
Comic. Doing a task using a company or organization’s website: [flowchart] Go to website, try to log in → Did it work? → Yes → Try to do your task. → Did it work? Yes → Nice! Done! If logging in did not work → Spend hours troubleshooting account / login. If that works, go to Try to do your task. If no → Give up and call customer service. If spending hours troubleshooting doesn’t work, also give up and call customer service. After calling customer service: Hold message: “Did you know you could do all this more quickly and easily on our website? Just go to w-w-w dot…” → Throw phone and laptop into the sea.
December 4, 2025 at 10:33 PM
Reposted by Geoff Wearmouth
zxvintage40.bsky.social
Popular Computing Weekly cover (12/12/1985)

READ: https://archive.org/stream/NH2021_Popular_Computing_Weekly_Issue851212.pdf#page/n00/mode/2up #zxspectrum #retrogaming
December 4, 2025 at 4:20 PM
Reposted by Geoff Wearmouth
webb-site.com
Breaking: remand prisoners in HK reach new record high
Only 54.5% of HK prisoners are convicted
dlvr.it
December 3, 2025 at 5:51 AM
Reposted by Geoff Wearmouth
theregister.com
Speccy clone storms back for Christmas without a shred of Sinclair code
Speccy clone storms back for Christmas without a shred of Sinclair code
Rubber-key revival leans on Linux, emulation, and third-party ROMs The Spectrum is an inexpensive home entertainment gadget from Retro Games Ltd (RGL) that's hauntingly similar to a totally unrelated 1980s home entertainment device that was loved by millions.…
dlvr.it
December 1, 2025 at 10:27 AM
warmtoffee.bsky.social
“The Spectrum” an iconic modern version of the 1982 classic ZX Spectrum, is now on sale in the UK for £59.99 at Amazon. A bargain and the default square root is my fast and accurate 2003 routine. Twenty games included but in my experience it runs everything.
The Spectrum has the original ZX Spectrum keyboard but you can use a USB keyboard. A bargain
November 23, 2025 at 5:59 PM
Reposted by Geoff Wearmouth
sinclairresearch.bsky.social
Ever wanted to know how your ZX81 ranked against a CRAY supercomputer from 1984? Assuming your eyesight is good enough, now you know.
Speed comparisons of many 1980s micros and Big Iron
November 13, 2025 at 4:37 PM
Reposted by Geoff Wearmouth
kevedwardsretro.bsky.social
Here's a Sinclair Microdrive cartridge with a UK pound coin for comparison. We trusted these mini-magnetic tape loops with our valuable data in the 1980s. Totally insane! To be fair, they were actually quite reliable. The tape loop is 5 metres long and stores a minimum of 85 to 100KBytes of data.
November 6, 2025 at 8:01 PM
Reposted by Geoff Wearmouth
webb-site.com
The Webb-site server will shut down on 31-Oct-2025
So is this the last that you will hear from me? Hopefully not! Read on. Source: Webb-site.com | Source date: 13-Oct-2025 20:15
dlvr.it
October 13, 2025 at 12:16 PM
Reposted by Geoff Wearmouth
kevedwardsretro.bsky.social
One of the most difficult BBC Micro books to obtain. Is there anyone out there that has a copy? I managed to get an ex-library copy that was re-bound. Curious to know how many are actually around. It was withdrawn from sale for legal reasons - it contained an annotated disassembly of BBC BASIC.
October 9, 2025 at 1:40 PM
warmtoffee.bsky.social
This is the most exciting ZX81 BASIC program ever. It runs on any Sinclair ZX81 model - TS1000 etc. It compares the upcoming LG81 ROM with the host ZX81 ROM.
This BASIC program should be downloadable soon but if you want to see how bad your ZX81 is get typing. Developed on iOS ZX81 by Kevin Palser.
The book ZX81 BASIC by Steven Vickers. My BASIC program generates a stream of random decimal fractions and then compares them to my faultless ZX81 ROM LG81 (Looking Glass ROM). The ZX81 numbers are half wrong, often by only one or two bits. When the screen is full, enter CONT to continue. The last few lines of my program. It took me less than an hour and I had to look up the address of VARS and the code for CHR$ “0”. Sample output. Only the Looking Glass ROMs can be all right all of the time.
October 8, 2025 at 7:18 PM
Reposted by Geoff Wearmouth
warmtoffee.bsky.social
Download The Looking Glass ZX Spectrum ROM V1.08 from

spectrumcomputing.co.uk/entry/44586/...

speccy4ever.speccy.org/_CMS.htm

ZX Spectrum ROMs and games.
Looking Glass - Spectrum Computing
Looking Glass for ZX-Spectrum 16K/48K (Geoff Wearmouth/UK, ?) by Geoff Wearmouth
spectrumcomputing.co.uk
October 5, 2025 at 8:13 PM
warmtoffee.bsky.social
This is the most revealing ZX Spectrum BASIC program ever. It runs on any Sinclair model - Spectrum, TS2068, or any clone.
It compares the error-free Looking Glass ROM v1.08 against the host ZX ROM. It should be downloadable by the weekend but if you want to see how bad it your Speccy is get typing.
The ZX Spectrum Introduction by Steven Vickers was an important step in computing around the world. There was however an error in the processing of binary fractions where half the fractions are out by one or two bits. My Looking Glass ROM version 1.08 perfects numbers by ditching an inappropriate BCD algorithm and using instead more of Steven Vickers’ Z80 code. This BASIC program compares the routine in my ROM with the routine in the computer that is hosting the program. The first part of my BASIC program. The last few lines of BASIC. The program generates a continuous stream of random numbers which are tested against my algorithm. If you see something interesting press BREAK. Example output. ZX numbers can be too high, too low or just right. Even then some of the perfect numbers occur where two wrong components cancel each other out. I am submitting this short program to download sites.
October 8, 2025 at 11:49 AM
warmtoffee.bsky.social
Remember in the 1980s when Sinclair and Amstrad dropped the price of The ZX Spectrum. Well RGL have continued the tradition and you can buy The Spectrum for £84.99 - 5% off. Just download the Looking Glass ROM V1.08 from Spectrum Computing or speccy4ever

www.smythstoys.com/uk/en-gb/gam...
speccy4ever.com
October 5, 2025 at 7:56 PM
warmtoffee.bsky.social
Back in 2014 Dr. Steve Vickers made some lecture slides available on his University website. I used his decimal to binary conversion routines to expand on a floating point display program I had typed in. This created a virtual computer with correct exponent and mantissa to test my ZX Spectrum ROMs.
The start of a comprehensive set of lecture slides from the ever fascinating Dr. Steve Vickers, author of the ZX81 and ZX Spectrum ROMs who was then teaching at Birmingham University. The entire lecture was instructive but the number conversion routines just visible at the bottom would be invaluable in building my virtual computer with always correct exponent and mantissa. Alas all his uplifting files have now been deleted following his retirement. ☹️
September 24, 2025 at 10:49 PM
Reposted by Geoff Wearmouth
samcoupe.com
The very brief mention of MGT's ZX Spectrum Emulator in the #SAMCoupe user guide here, being called "a special program". For the initial emulator MGT had to create a compatible #ZXSpectrum ROM from scratch, as the actual ZX ROM's copyright was held by Amstrad. The compatible ROM wasn't fully...
September 22, 2025 at 6:08 PM
warmtoffee.bsky.social
The Looking Glass ROM V1.08 for the 48K ZX Spectrum is now available for download with documentation.

speccy4ever.speccy.org/_CMS.htm

This is the most accurate ROM ever available for the ZX Spectrum and is the equal to Microsoft Binary Format 9-digit BASIC. Say goodbye to dodgy figures.
Some of the numerous ZX Spectrum ROMs available from the site of Davide Barlotti Microsoft 9-digit BASIC examples from Wikipedia. LG18 matches them all except for that red logarithm. Original 1982 square roots don’t match Microsoft’s GW-BASIC hex values $35 $04 $F3 $34. The Looking Glass ROM now does. The new LG18 ROM matches the C64 with 138.375
September 23, 2025 at 11:45 AM
Reposted by Geoff Wearmouth
karlfl.bsky.social
I am no accountant, but this seems very wrong #PostOfficeScandal www.computerweekly.com/news/3666313...
‘Utter madness’ as Post Office paid law firm double the cost of scandal public inquiry | Computer Weekly
The Post Office legal representation at public inquiry into Horizon scandal cost twice as much as the actual inquiry
www.computerweekly.com
September 15, 2025 at 12:31 PM